Conventionally, as disclosed in Patent Document 1, a refrigeration cycle device has been proposed that is applied to air conditioners for vehicles and which can be configured to switch a refrigerant circuit. Specifically, the refrigeration cycle device is capable of switching among a refrigerant circuit for an air cooling mode of cooling the vehicle interior as a space to be air-conditioned, a refrigerant circuit for an air heating mode of heating the vehicle interior, and a refrigerant circuit for a dehumidification heating mode of heating and dehumidifying the vehicle interior.
More specifically, the refrigeration cycle device described in Patent Document 1 has a plurality of heat exchangers, including an interior condenser, an exterior heat exchanger, and an interior evaporator. The interior condenser exchanges heat between ventilation air and a high-temperature and high-pressure refrigerant discharged from a compressor. The exterior heat exchanger exchanges heat between the outside air and a refrigerant on the downstream side of the interior condenser. The interior evaporator exchanges heat between the ventilation air and a low-pressure refrigerant on the downstream side of the exterior heat exchanger.
In the air cooling mode, the refrigeration cycle device switches to the refrigerant circuit that evaporates the refrigerant at the interior evaporator while dissipating heat from the refrigerant at the exterior heat exchanger. In the air heating mode, the refrigeration cycle device switches to the refrigerant circuit that evaporates the refrigerant at the exterior heat exchanger while dissipating heat from the refrigerant at the interior condenser.
Further, in the dehumidification heating mode, the refrigeration cycle device switches to the refrigerant circuit that evaporates the refrigerant at the interior evaporator while dissipating heat from the refrigerant at both the interior condenser and the exterior heat exchanger. Thus, in the dehumidification heating mode, the ventilation air cooled and dehumidified by the interior evaporator is reheated by the interior condenser to achieve the dehumidification heating of the vehicle interior.
The refrigeration cycle device disclosed in Patent Document 1 further includes an internal heat exchanger that exchanges heat between the refrigerant flowing out of the exterior heat exchanger and the refrigerant flowing out of the interior evaporator.
In the air cooling mode and the dehumidification heating mode, the internal heat exchanger exchanges heat between the high-pressure refrigerant flowing out of the exterior heat exchanger and the low-pressure refrigerant flowing out of the interior evaporator. Thus, a difference in enthalpy (refrigeration capacity) between the refrigerant at the outlet side of the interior evaporator and the refrigerant at the inlet side thereof is increased to improve the coefficient of performance (COP) of the cycle.